Monitoring device for printer

ABSTRACT

A monitoring device is described for a printer, especially a sheet-fed offset printer, with a controller that records the signals of signal transmitters in the individual units of the printer, through which command signals for actuators/drives connected to the control can be generated as a function of the signal state, and a monitoring computer that additionally records the signal states of the signal transmitters and causes the switching off of actuators/drives. The task of the following invention is to modify such a monitoring device so that a device is obtained that permits error-proof and, especially, differentiated actions during malfunctions. A variant according to the invention consists of the fact that the signal states of the signal transmitters (G) are fed to several slaves (S) designed as computers, which are connected to each other via a bus (UB) and to a monitoring master (UM) connected upstream from a monitoring computer (UR), and that the actuators/drives A are connected to one of the slaves (S) and can be switched off with a command sent by the monitoring master (UM) via bus (UB).

DESCRIPTION

[0001] The invention concerns a monitoring device for a printer according to the preamble of claim 1.

PRIOR ART

[0002] Sheet-fed offset printers have a number of units, such as the feeder, delivery device, printing groups, coating and processing devices. Different operating elements in the form of control switches are provided to operate these individual units and the printer as a whole, through which machine operation, certain operational functions, etc., can be initiated. The moving elements, such as cylinders and rollers, are protected by protection elements movable for maintenance purposes, in order to prevent the operator from being exposed to danger from a running machine due to an open protection circuit. The protection elements are protected by sensors and switch elements designed as limit switches. The signals of the operating elements in the individual units, as well as the sensors and switches that protect the individual protection systems, are connected to one or more stations, forming the controller of the printer, which are preferably configured as a computer. A controller, which consists of at least one computer and that records the signal states of the different control elements and protective switches, is known from DE 43 27 848 A1 and EP 0 243 728 A2. DE 195 27 089 A1 and 195 20 918 A1 describe the individual units of the stations designed as a computer and connected to the printer, which combine to form the controller of the printer.

[0003] As is known from DE 43 27 848 A1 and EP 0 243 728 A2, certain functions of a printer must be protected redundantly, i.e., the activation of a control element or the opening of a protection system causes the immediate shutdown of the corresponding drive, especially the main drive of the printer. As a result, the signals of the corresponding operating element and the switches that protect the protection system are fed both to the controller and, parallel to it, to a monitoring device configured as a computer. Switching of the drive or drives as a function of the signal state then occurs both via the controller and via the monitoring device. Shutdown therefore also occurs during failure of the controller.

[0004] The variety of operating elements and safety elements (switches, sensors) results in high cabling expense due to the redundant monitoring of the signal transmitters. The high cable expense also hinders the search for errors during cable defects or malfunctions in the corresponding plug-in connectors.

[0005] The large number of operating and protection elements to be monitored (switches, sensors) also causes a high computer load on the monitoring system. This is especially true, since it must be guaranteed by the controller and by the monitoring system that a specific reaction, especially shutdown (stopping) of the printer, occurs within a stipulated interval at specified signal states.

OBJECTIVE OF THE INVENTION

[0006] The objective of the following invention is therefore to modify a monitoring device according to the preamble of claim 1, so that a device is provided that makes possible error-proof and especially, differentiated actions in the event of a malfunction, while avoiding the aforementioned shortcomings.

[0007] This objective is realized by the features of claim 1. Modifications of the invention are apparent from the dependent claims.

EXAMPLE

[0008] It is proposed according to the invention that the monitoring device haven bus system, via which several computers that enter the signal states of the operating elements, switches and sensors and function as slaves are connected to a master computer. Commands to enter the input (signal state) are repeatedly sent to the individual slaves via the bus system by the master connected to the actual monitoring computer. In response to a command, the individual slaves send an indicator of the inputs present in them (signal states of the operating elements, switches, sensors). The master, connected after the monitoring computer, thus obtains, on each query, an indication of all the input states in the individual units to which the slaves of the monitoring device according to the invention are assigned. The monitoring computer then generates, from its overall input indication, switching commands for the drives and actuators being monitored. If a state results from the input indication entered by the master, based on which a drive or actuator, and especially the main drive of a printer, is to be stopped, this command is sent via the bus system to the corresponding slave in the corresponding unit. The slave receiving this command then causes switching off or stopping of the actuator/drive.

[0009] Due to the fact that the monitoring computer is connected via a master and the bus system to the individual units of the slaves assigned to the printer, a noticeable simplification in cabling expense is produced, since only one shielded line is necessary for the serial bus system. As an additional advantage, a situation is obtained in which a simultaneous indication of all the switching states of the operating elements, sensors, switches recorded by the slaves is available to the monitoring computer, as the result of each query cycle. Therefore, interdependent switching states (signal states) can be determined, and the entire printer and the switching states of signal transmitters mounted on the printer can be monitored.

[0010] Since the switching on/off of actuators/drives in the event of a malfunction occurs through a slave of the monitoring system assigned to the corresponding unit, measures adapted to the corresponding hazardous situation being protected against can be introduced. Upon the opening of a protection system between the individual printing groups, the slave assigned to the main drive would shut down the printer drive from a master command and therefore stop the operation of the printer itself. If, for example, only a protection system assigned to the ink duct were open during machine operation and print production, to avoid a hazardous situation (feed site), it may be sufficient merely to shut down the corresponding drive (for example, the drive of the duct roller). Interruption of the entire printing process and thus ink flow into the individual printing groups can be avoided in such a situation. Restarting of the machine with a correspondingly large number of wasted sheets is thus unnecessary. After closure of the corresponding protection system and possibly acknowledgment by an operating person, the drive shut down by the monitoring system according to the invention can be switched on again, so that the ink flow malfunction, occurring only briefly in the printing group, if at all, only causes a small number of wasted sheets.

[0011] Switching off of the corresponding components occurs via the slave of the monitoring system assigned to the unit. This slave receives the command to shut down from the master assigned to the monitoring computer as a function of evaluation of the queried switch signal states fed to the master. Individual switching off of actuators and drives during failure of one or more components of the control is thus possible by the monitoring system according to the invention.

[0012] According to a preferred variant of the invention, it is proposed that the slaves assigned to the monitoring system monitor the cyclical query of the master via a software routine. If a query order from the master is absent within a stipulated time interval (which can be caused, for example, by a malfunction in the bus system or a malfunction in the master), switching off of the actuator/drive assigned to the slave or the entire printer (main drive) occurs. Malfunctions in the bus system between the master and the slaves can therefore be monitored, based on errors in signal transmission.

[0013] According to another preferred variant of the invention, it is proposed that each slave assigned to the stations of the unit additionally have a hardware timeout (watchdog). In addition to software monitoring of command signals coming from the master, monitoring of the bus that connects the slaves to the master also occurs. Here again, in the absence of a master signal within a stipulated time interval, shutdown of the prescribed actuators, drives or the entire printer occurs.

[0014] An embodiment of the invention will now be explained with reference to the single drawing. The drawing shows, in principle, a sheet-fed offset printer with a decentralized control, as well as the monitoring system made up of a master and slaves.

[0015] The sheet-fed offset printer D, depicted in the figure, has a feed device, a delivery device, and printing groups. Stations ST, configured as a computer and forming the overall controller, are connected to the individual units of this printer D. The entering of signals of signal transmitters G arranged in the delivery device thus occurs via the station (computer) ST connected to the delivery device of the printer D. In the interest of clarity, only one signal transmitter G connected to a station ST is shown in the figure. The signal transmitters G in the individual units of the printer D can be sensors, switches, operating elements, control switches, etc.

[0016] Control of actuator/drives A arranged in the corresponding unit also occurs in the individual units in printer D via the individual computers of stations ST. Here again, for simplicity, only one actuator/drive A connected to a station ST is shown.

[0017] The individual stations ST are connected to each other via a bus SB, so that switching operations corresponding to the sheet run can be performed in the individual units of the printer D. The stations ST are also connected via bus SB to the control station LS of the printer D.

[0018] A slave S is connected as computer to each station ST of the printer D, which is connected via a common serial bus system UB to another computer UM, designed as a master. The master computer UM communicates with a monitoring computer UR. The signal transmitters G in the individual units, as well as the actuators/drives A, also communicate with the stations ST by a corresponding input card with slaves S. An operating state of the signal transmitter G can therefore be recorded both by the control ST and by the slave S.

[0019] The monitoring master UM connected to the monitoring computer UR sends cyclical query commands to the individual slaves S via the monitoring bus UB. Thereupon, each of the slaves S enters the signal states of the connected signal transmitters G via the input cards. An indication of the signal states of transmitters G is sent back by each slave S via the monitoring bus UB to the monitoring master UM, so that the presence of permitted, unpermitted states can be determined via the monitoring computer UR from the indication of these state signals of all transmitters G. If it is found by the monitoring computer UR that a protective grid is opened, for example, during the running of the machine, the monitoring master UM sends, via the monitoring bus UB, a signal to the corresponding slave (main drive), in order to stop the printer. Switching off of the corresponding drive A then occurs via the slave S connected to it.

[0020] Software and/or hardware timeouts are provided in the individual slaves S, so that, in the absence of a corresponding query signal from the monitoring master UM, automatic shutdown of the actuators/drives A of slave S occurs.

[0021] List of Reference Characters

[0022] D Printer

[0023] ST Station/station computer

[0024] SB Control bus

[0025] LS Control station

[0026] G Signal transmitter

[0027] A Actuator/drive

[0028] S Slave

[0029] UR Monitoring computer

[0030] UM Monitoring master

[0031] UB Monitoring bus 

1. Monitoring device for a printer, especially sheet-fed offset printers, with a controller that records the signals of signal transmitters in the individual units of the printer, through which command signals for actuators/drives connected to the controller can be generated as a function of the signal state, and a monitoring computer that additionally records the switching states of the signal transmitters and causes switching off of actuators/drives, characterized by the fact that the signal states of the signal transmitters (G) are fed to several slaves (S) designed as computers, which are connected to each other via a bus (UB) and to a monitoring master (UM) connected upline from the monitoring computer (UR), and that the actuators/drives (A) are connected to one of the slaves (S) and can be switched off with a command sent by the monitoring master (UM) via bus (UB).
 2. Monitoring device according to claim 1, characterized by the fact that the bus (UB) is designed as a serial bus system.
 3. Monitoring device according to claim 1 or 2, characterized by the fact that cyclical commands for entering and transmitting signal states of the signal transmitters (G) by the slaves (S) are sent via bus (UB) and master (UM).
 4. Monitoring device according to one of the preceding claims, characterized by the fact that monitoring of signals sent by the slaves (S) on bus (UB) occurs by master (UM).
 5. Monitoring device according to claim 4, characterized by the fact that, in the absence of a command from master (UM) on bus (UB), the switching off by the slaves (S) occurs.
 6. Monitoring device according to claim 5, characterized by the fact that monitoring is implemented by means of software in slaves (S).
 7. Monitoring device according to claim 5, characterized by the fact that monitoring is implemented by means of hardware in slaves (S).
 8. Monitoring device according to one of the preceding claims, characterized by the fact that all input signals can be entered synchronously at one time by slaves (S). 